A novel characteristic of baculovirus infection is the unusual and abundant induction, synthesis and assembly of cellular membranes, particularly in the nucleoplasm. The molecular strategy utilized by the baculovirus to obtain an envelope is quite unique. De novo membrane assembly in the nucleoplasm has been hypothesized as the process for the elaborate induction of intranuclear membranes; however, this theory is not consistent with current models of eukaryotic cell membrane assembly and lipid biosynthesis. Our studies identify several PDV envelope proteins and one of these, PDV-E66, is present in intranuclear microvesicles and the viral envelope. This is the first biochemical evidence that the nuclear microvesicles function as a source or an intermediate of the PDV viral envelope. The identification of PDV envelope proteins provide markers to allow the biosynthesis, trafficking and assembly of membranes which occur in the infected cell nucleoplasm. Our observations and preliminary data suggest that the Autographa californica nuclear polyhidrosis baculovirus may encode homologs of key cellular proteins that may function to influence inner nuclear membrane activities and de novo lipid synthesis. This study may not only reveal the novel envelopment strategies utilized by AcMNPV but could also reveal new details of eukaryotic cellular pathways of transport and nuclear membrane biogenesis. AcMNPV has become the most extensively studied baculovirus because of its use as a cloning and expression vector and its use and development for crop protection as a natural or genetically engineered microbial pest control agent. The biology of baculovirus-host interactions is uniquely complex yet studies of this virus-hose system are serving an important role in the development of fundamental knowledge of molecular and biochemical pathways in insects and invertebrates for comparison with the more comprehensively studied vertebrate systems. These studies are relevant to the very significant role that invertebrates play in the transmission of disease to plants, animals and humans and for their use in pest control strategies fundamental to crop protection and public health.